async-camping.rb

require 'camping'

Camping.goes :Async

module Async
  def service(*a)
    return super unless respond_to?(:async?)

    EM.next_tick do
      send(@method, *a)
    end

    throw :async
  end
end

module Async::Helpers
  class DeferrableBody
    include EventMachine::Deferrable

    def call(body)
      body.each do |chunk|
        @body_callback.call(chunk)
      end
    end

    def each &blk
      @body_callback = blk
    end
  end
  
  ASYNC_CALLBACK = 'async.callback'.freeze

  def stream
    @body = []
    @stream ||= DeferrableBody.new
    res = to_a
    res[2] = @stream
    @env[ASYNC_CALLBACK].call(res)
  end

  def push(body)
    body = Array(body) unless body.respond_to?(:each)
    @async.call(body)
  end

  def finish(str = "")
    if @stream
      @async.succeed
    else
      @body ||= str
      @env[ASYNC_CALLBACK].call(to_a)
    end
  end
end

module Async::Controllers
  def self.A(*r)
    R(*r).class_eval do
      def async?; true end
      self
    end
  end

  # Inherit from A to create async response
  class Index < A '/'
    def get
      EM.add_timer(2) do
        # Call #finish to render stuff
        finish render(:index)
      end
    end
  end

  class Push < A '/push'
    def get
      # Call #stream to start a streaming response
      stream

      EM.add_timer(1) do
        # Push stuff out
        push "Hello\n"
      end

      EM.add_timer(2) do
        # Push more stuff
        push render(:index)
        # Call #finish to close
        finish
      end
    end
  end
end

module Async::Views
  def index
    p 'Hello'
  end
end